Plasma gun having a hydrogen storing reservoir



June 18, 1968 A. M. BENSUSSAN ET AL 3,389,289

PLASMA GUN HAVING A HYDROGEN STORING RESERVOIR I Filed Aug. 51, 1965 2 Sheets-Sheet '1 F IG.] PRIOR ART "E; 7 g 7 28 d 4 A. I

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MODULATOR PHASE SHIFT NETWORT INVENTORS Andr-Maw flmuumw Wm flax illa) BY J ATTORNEY June 1968 A. M. BENSUSSAN ET AL PLASMA GUN HAVING A HYDROGEN STORING RESERVO-IR 2 Sheets-Sheet 2 Filed Aug. 31, 1965 INVENTORS Arid/" Mmm flemswam Wes fm wiilan BY hfilw I ATTORNEY 3,389,289 PLASMA GUN HAVING A HYDROGEN STORING RESERVOIR Andre Marc Bensussan, 57 Ave. de Sutfren, Paris, France,

and Yves Papillon, 27 Ave. de la Gilquiniere, Morsangsur-Orge, France Filed Aug. 31, 1965, Ser. No. 483,991 Claims priority, application France, Sept. 7, 1964,

5 Claims. Cl. 313-480) ABSTRACT OF THE DISCLOSURE The present invention relates to a plasma gun having a hydrogen reservoir consisting of powdered titanium hydride which is agglomerated with an insulating binder material also in powder form. Electrodes are arranged to form a spark gap adjacent to said hydrogen reservoir. When the electrodes are energized with a predetermined potential, an electrical discharge occurs across said spark gap which contacts the hydrogen reservoir and ionizes gas released therefrom to form a burst of plasma.

This invention relates to plasma guns for the production of plasmas of high density and high ion intensity, in view of the increasingly widespread interest being shown in the field of plasma formation by reason of its constantly extending range of applications.

As is in fact already known, such applications include research on controlled thermonuclear fusion, space propulsion, re-entry of satellites into the earths atmosphere, and so forth.

One plasma gun of known type is the Marshall gun shown in FIG. 1 of the accompanying drawings. A highspeed valve 4 injects a burst of gas into the gun 2 at the moment when the charge voltage of a capacitor bank 8 (not shown) is applied between the coaxial electrodes 10 and 12 by means of a ring 6 of coaxial cables (only two of which are shown in the figure). A discharge is then established between said electrodes. If the term Tis employed to designate the plasma current and the term E is employed to designate the magnetic field which is produced by said current, the plasma 15 is subjected to a force P which is represented by the product TXF, with the result that said plasma is driven towards the l1dS50f the coaxial conductors (towards the right in the case of the figure).

In these plasma guns as in those of the so-called spiral type, gas must be introduced therein and the operating pressure of these plasma guns corresponds to the minimum of the Paschen curve (approximately 1.33 Pa) by reason of the fact that the gas must be ionized. It is therefore impossible to make use of plasma guns of this type for the purpose of triggering a vacuum spark-gap since the requisite pressure is too high for the triggering voltage applied to the spark-gap to have an appreciable value. In the plasma gun referred to, the quantity of gas introduced is calibrated by means of a quick-opening valve 4, thus resulting in low precision in the instant of initial emission of the burst of gas.

A plasma gun which serves to overcome the disadvantages of the type referred-to above is illustrated in FIG. 2, and is essentially made up of a stack of washers 16 of hydrogenated titanium and insulating washers 18 arranged in alternate sequence. During operation, discharges take place between the successive titanium washers.

A capacitor bank 20, the discharge of which is triggered by a spark-gap 22 serves to apply between the electrodes 24-26 a voltage pulse of fairly long duration. The plasma gun is triggered when a short voltage pulse is applied between electrodes 28 and 24. It should be noted that the i Pte 3,389,282? Patented June 18, 1968 operation of the spark-gap is determined by the application to its starting electrode 30 of a pulse produced by the modulator 32. Said modulator controls the modulator 34 which produces the pulses for triggering the plasma gun. through the intermediary of a phase shifter 36. In order to obtain satisfactory operation of the plasma gun, it. is necessary to ensure accurate regulation of the pulses applied to the tube and consequently entails the use of a circuit which proves difficult to develop.

This source, known as the Bostick source, as well as other sources which have been designed and developed by the same inventor make use of the property of titanium in which hydrogen is retained in the occluded state. However, the necessary hydrogenation process is difficult to carry into practice if it is desired to hydrogenate the titanium. in depth rather than limit the process to a surface hydrogenation. In such a case, the titanium is converted to powdered titanium hydride which no longer has suflicient me chanical strength. Moreover, the occluded hydrogen in parts formed of titanium becomes rapidly depleted when the plasma gun is in operation. The construction of a titanium wafer gun is therefore difficult since it proves neces sary to divide the conductive metal in such amanner as to produce a discharge which contacts the titanium. The stack of alternately arranged titanium washers and insulating washers provides a partial solution to the problem but it is not possible to maintain the geometrical dimensions of the plasma gun components during hydrogenation. Finally, it has already been explained that the operation of the plasma gun calls for the use of three electrodes and that the application of two triggering pulses to said electrodes entails the use of a complicated electrode which constitutes an obstacle to the practical utilization of this gun.

The plasma gun in accordance with the invention also turns to profitable account the chemical properties of titanium and is not object to the disadvantages of the known devices which have been discussed in the foregoing.

A plasma gun in accordance with the invention is characterized in that it makes use of a hydrogen reservoir constituted by powdered titanium hydride which is agglomerated by means of an insulating hinder, the quantity of binder employed being determined according to the particle size distribution of the hydride.

According to one embodiment of the invention, the insulating binder consists of araldite which is a plastic material of the ethoxylin resin type. On the other hand the powdered titanium hydride can be mixed with powders comprising the starting products of a ceramic material. The aggregate is then sintered to form a reservoir of ceramic material containing titanium hydride.

According to a first alternative form of the invention, the member which performs the function of hydrogen reservoir has the shape of a cylindrical sleeve, thus en abling the construction of a gun of the axial ejection type.

Finally, according to another alternative form, the hy drogen reservoir is made up of two coaxial cylindrical sleeves placed one above the other at a small distance apart, the two opposite faces of said sleeves being outwardly divergent. This arrangement is favorable to the construction of a plasma gun of the lateral ejection type.

Aside from the main arrangements which have just been outlined, reference will be made in the following description to secondary arrangements relating essentially to the design of plasma guns.

The novel nature of the active portion of the hydrogen reservoir from which the ions are extracted readily permits of numerous geometries, thereby considerably increasing the potential uses of a source of this type.

Lastly, as each burst of plasma is ejected, the discharge comes into contact with the hydride which is incorporated in the binder. Surface erosion and automatic regeneration of the ion carriers take place. It is the mass as a whole assazsa which contains the ion carriers whereas in the case of plasma guns of known type (washer-type guns) hydrogenation was superficial.

The characteristic features of this invention will become more readily apparent from the following description of two forms of embodiment which, as will be understood, are not intended to set any limitation either on the mode of operation of the invention or on the potential applications thereof.

FIG. 1 illustrates a plasma gun of the Marshall type.

FIG. 2 illustrates a plasma gun of the titanium washer type.

FIGS. 3 and 4 illustrate plasma guns of the axial ejection and lateral ejection type.

The body of the gun of FIG. 3 comprises a tubular member of generally cylindrical configuration and formed of an insulating material such as araldite. A metal plate 42 closes off the gun at the rear end. A conducting member 43 having the. shape of a cylindrical sleeve is secured to the insulating member 40 and adapted thereto. Said member is provided with a lateral annular flange 45 which serves to secure the gun in position. A metal cylinder 44 is disposed within the central opening of the gun and fitted with a base 46 which is pierced by a central opening. An assembly of a number of coaxially arranged members is applied against said base 46 and consists of electrodes 48 and 50 having the shape of a cylindrical sleeve. Between said electrodes are fitted a mica washer 52 and a block 54 which performs the function of a hydrogen reservoir. Said block, which has the shape of a sleeve, is formed of powdered titanium hydride which is agglomerated by means of araldite, the quantity of this insulating material being determined according to the particle size distribution of the hydride. Central openings formed in the members 48, 50, 52, 54 define the space in which the plasma is generated. It should be noted that the external diameter of the block 54 is smaller than the external diameter of the electrodes since an araldite sleeve 56 is fitted over said member 54.

Said plasma gun operates without any need for a third triggering electrode. The voltage of a capacitor bank is directly applied between the two electrodes 48 and 50, the discharge comes into contact with the inner face of the araldite-agglomerated hydride block 54. The outer face of said block is bonded to the araldite sleeve 56 in such a manner as to ensure that the discharge path is well defined. The function of the mica washer 52 is similar to that of the sleeve 56. The voltage between the two electrodes 48 and 58 is withstood by the insulator 40. The elimination of the triggering electrode results in a simplification of the associated electronic circuitry. Apparatus for providing synchronization between the triggering pulse of the plasma gun and the triggering pulse of the spark-gap which supplies the main discharge accordingly serves no further purpose.

FIG. 3 which has just been described illustrates a gun for axial plasma ejection whilst FIG. 4 relates to a plasma gun 57 of the lateral ejection type. In this latter case a burst of plasma is formed when the discharge which is established between the concentric electrodes 58 and 60 comes into contact with the hydride blocks 62, 64 which are agglomerated by araldite and which constitute identical coaxial rings centered on the electrode 60. Blocks 66 and 68 are fabricated of an insulating material. and act as supports for the electrodes and reservoir elements. The coaxial rings or sleeves 62, 64 are placed at a small distance from each other, the two opposite faces thereof being outwardly divergent.

It should be noted that the invention also applies to the design of a plasma gun in which the ejector tube has an intermediate opening between 0 (axial ejection) and (lateral ejection).

What we claim is:

1. In a plasma gun,

a pair of electrodes spaced apart to define a spark gap and adapted to be energized by an electrical voltage source,

a hydrogen reservoir of powdered titanium hydride agglomerated with an insulating binder, located between said electrodes adjacent to said spark gap, and

support means of insulating material partially surrounding said reservoir and said electrodes,

whereby the application of a voltage of a predetermined level will cause a spark discharge between said electrodes to form a burst of plasma.

2. A plasma gun as described in claim 1 wherein said hydrogen reservoir is formed of powdered titanium'hydride agglomerated with a plastic binder of the ethoxyline resin type.

'3. A plasma gun as described in claim 1 wherein said hydrogen reservoir comprises a ceramic material containing titanium hydride.

4. A plasma gun as described in claim 1 wherein the hydrogen reservoir comprises a cylindrical sleeve supported intermediate said electrodes whereby the spark discharge between said electrodes; occurs through the hollow center portion of said. sleeve.

5. A plasma gun as described in claim 1 wherein the hydrogen reservoir comprises two cylindrical sleeves oriented end to end and being spaced apart whereby said spark gap is bounded by opposed end wall portions of said sleeves, one of said electrodes extending through the hollow center portions of said sleeves and the other of said electrodes extending adjacent outer surfaces of said sleeves near said opposed end wall portions.

References Cited UNITED STATES PATENTS 2,900,548 8/ 1959 Bostick 313-23 3,290,542 12/1966 Lafferty 313--l78 FOREIGN PATENTS 160,486 1/1955 Australia.

JAMES W. LAWRENCE, Primary Examiner.

STANLEY D. SCI-ILOSSER, Examiner.

R. L. JUDD, Assistant Examiner. 

